The invention relates to apparatus for forming circularly bent ring members from elongated metal profiled strip material, particularly for making rims of spoke wheels such as bicycle wheels.
In the conventional methods of forming bicycle wheel rims an elongated profiled strip of, for example, steel or aluminum is introduced into a three-roll rolling apparatus and bent into a spiral comprising a plurality of convolutions. Thereafter, the feed end portion of the spiral is cut-off, and strip lengths equal to the circumferential length of the rims to be formed are cut from the spiral and the ends of these strip lengths are welded together. Thereafter, the spoke receiving holes are drilled in the rim, and subsequently, the rim is polished. This method has the disadvantage that it can only be performed by skilled personnel, and that the manufacture, for instance by extrusion, of the extended profiled strip material and the forming of the circularly bent rims therefrom must be carried out in the same factory if the uneconomical transport of the profiled strip material of great length is to be avoided. Another disadvantage of the known methods is that in connecting the ends of the rim pieces cut from the spirally bent profiled strip these ends have to be transversely bent towards each other whereby stresses and consequently lateral deformations may occur in the formed rim which must be corrected later when the spokes are tensioned.